1. Field of the Invention
The present invention relates generally to a circuit board connecting device, and more particularly to an improvement in a circuit board connecting device which is used for putting first and second groups of circuit terminals provided respectively on a couple of separate circuit boards in mutual electrical connection so that the separate circuit boards are electrically connected with each other under a condition wherein one of the separate circuit boards is closely laid on top of the other of the separate circuit boards.
2. Description of the Prior Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Various kinds of electric or electronic parts are built even in a relatively small-sized electronic apparatus such as a mobile phone or the like. A major part of those parts are dispersedly mounted on, for example, a couple of separate circuit boards to fulfill their respective functions. In the relatively small-sized electronic apparatus, having an eye to the couple of separate circuit boards on which the electric or electronic parts are mounted, it is likely that one of the separate circuit boards is required to be closely laid on top of the other of the separate circuit boards for reducing a space occupied thereby when the separate circuit boards are electrically connected with each other. Such electrical connection between the separate circuit boards wherein one is closely laid on top of the other is hereinafter referred to as electrical piled-up connection.
In general, when a plurality of circuit boards, such as solid circuit boards or flexible printed circuit boards (FPCs), are electrically connected with one another, a plurality of electrical connectors are mounted on the circuit boards, respectively, and one of the electrical connectors is engaged with another electrical connector so as to connect one of the circuit boards electrically with another circuit board. In case of the electrical piled-up connection mentioned above, first and second electrical connectors are mounted respectively on the separate circuit boards to be engaged with each other. The first electrical connector is formed into a plug type connector and the second electrical connector is formed into a receptacle type connector to be a mate electrical connector for the first electrical connector, so that the plug type connector is engaged with the receptacle type connector when the separate circuit boards are put in a condition of the electrical piled-up connection.
Under such a situation, there have been previously proposed several circuit board connecting devices, each of which is used for putting a couple of circuit boards in the electrical piled-up connection, as disclosed in, for example, the Japanese patent application published before examination under publication number 2000-260509 (hereinafter, referred to as published prior art document 1) and the Japanese patent application published before examination under publication number 2004-55306 (hereinafter, referred to as published prior art document 2).
A circuit board connecting device (a board-to-board connecting system) disclosed in the published prior art document 1 comprises a first connector (a connector piece (100)) mounted on a surface of a first circuit board (a board (110)) so as to be fixed to the first circuit board and a second connector (a connector piece (200)) mounted on a surface of a second circuit board (a board (210)) so as to be fixed to the second circuit board, wherein the first and second circuit boards are to be subjected to the electrical pile-up connection. The first connector is provided with a plurality of first contacts (contacts (120)) arranged on a housing (130) and the second connector is provided with a plurality of second contacts (contacts (220)) arranged on a housing (230). Each of the first contacts has a top end portion thereof folded back in the shape of U to be resiliently transformed.
When the surface of the first circuit board on which the first connector is mounted is caused to be opposite to the surface of the second circuit board on which the second connector is mounted so that the first circuit board is closely laid on top of the second circuit board, the first and second connectors are coupled with each other and the top end portion of each of the first contacts of the first connector comes into contact with a corresponding one of the second contacts of the second connector. Thereby, the first contacts of the first connector are connected respectively with the second contacts of the second connector and the first and second circuit boards are put in a condition of the electrical piled-up connection.
With the first and second circuit boards thus put in the condition of the electrical piled-up connection, since the top end portion of each of the first contacts of the first connector, which is folded back in the shape of U to be resiliently transformed, is put in press-contact with the corresponding one of the second contacts of the second connector with resilient transformations thereof, it is expected that the first and second contacts are surely connected with each other.
Then, a circuit board connecting device (a board connecting connector) disclosed in the published prior art document 2 comprises a first connector (a plug connector (24)) mounted on a surface of a first circuit board (a printed circuit board (26)) so as to be fixed to the first circuit board and a second connector (a receptacle connector (20)) mounted on a surface of a second circuit board (a printed circuit board (22)) so as to be fixed to the second circuit board, wherein the first and second circuit boards are to be subjected to the electrical pile-up connection. The first connector is provided with a plurality of first contacts (contact terminals (28Ai), (28Bi)) arranged on a first housing (a base portion (24M)) and the second connector is provided with a plurality of second contacts (contact terminals (34Ai), (34Bi)) arranged on a second housing (a base portion (20M)). An engaging hook (30N) is formed on a coupling portion (30m) of a supporting member (30) pressed in the first housing of the first connector and a projection (32mn) is formed on a resilient tongue portion (32mr) of a supporting member (32) pressed in the second housing of the second connector.
When the surface of the first circuit board on which the first connector is mounted is caused to be opposite to the surface of the second circuit board on which the second connector in mounted so that the first circuit board is closely laid on top of the second circuit board, the first and second connectors are coupled with each other and each of the first contacts of the first connector comes into contact with a corresponding one of the second contacts of the second connector. Thereby, the first contacts of the first connector are connected respectively with the second contacts of the second connector and the first and second circuit boards are put in a condition of the electrical piled-up connection.
With the first and second circuit boards thus put in the condition of the electrical piled-up connection, the engaging hook (30N) formed on the coupling portion (30m) of the supporting member (30) pressed in the first housing of the first connector is put in engagement with the projection (32mn) formed on the resilient tongue portion (32mr) of the supporting member (32) pressed in the second housing of the second connector so as to prevent the first housing of the first connector from being separated from the second housing of the second connector. Thereby, the first contacts of the first connector and the second contacts of the second connector are stably connected with each other and consequently it is expected that the electrical piled-up connection between the first and second circuit boards is stably maintained.
In each of the previously proposed circuit board connecting devices used for putting a couple of circuit boards in the electrical piled-up connection as described above, there are the following defects or disadvantages.
In the case of the circuit board connecting device disclosed in the published prior art document 1, any locking means or holding means for preventing the first housing of the first connector from being separated from the second housing of the second connector under a condition wherein the first and second connector are coupled with each other is not provided. Accordingly, when undesirable external force acts on one or both of the first and second connectors coupled with each other, for example, the first contacts of the first connector and the second contacts of the second connector are put in unstable mutual connection and consequently it is feared that the electrical piled-up connection between the first and second circuit boards is not stably maintained.
Further, in the case of the circuit board connecting device disclosed in the published prior art document 2, the engaging hook (30N) which is formed on the coupling portion (30m) of the supporting member (30) pressed in the first housing of the first connector and the projection (32mn) which is formed on the resilient tongue portion (32mr) of the supporting member (32) pressed in the second housing of the second connector and with which the engaging hook (30N) engages, are so provided as to be locking means or holding means for preventing the first housing of the first connector from being separated from the second housing of the second connector under a condition wherein the first and second connector are coupled with each other. However, the engaging hook (30N) cannot be operative to engage firmly with the projection (32mn) because of structural limitations in each of the coupling portion (30m) of the supporting member (30) on which the engaging hook (30N) is formed and the resilient tongue portion (32mr) of the supporting member (32) on which the projection (32mn) is formed. Accordingly, when undesirable external force acts on one or both of the first and second connectors coupled with each other, for example, the engaging hook (30N) disengages easily from the projection (32mn), so that the first contacts of the first connector and the second contacts of the second connector are put in unstable mutual connection and consequently it is feared that the electrical piled-up connection between the first and second circuit boards is not stably maintained.